Glyph of Watchful Eye

Ok I've been trying this glyph out, because of its potential to warrior tanking yet after a few attempts and a test with a friend the glyph seemingly does nothing. I still need to target a player, I am wondering if this is a bug or not, or does the player need to be below a certain % of health for it to work.
Also I have made sure they're within 25 yards, and tried it with both Safeguard and Intervene, both not working without me targeting someone.

I find Intervene to be more and more a tool to move from point A to point B quicker rather than something to protect someone else with. As a warrior you already take a crapload of damage from everything and soaking a whole swing from someone else can get you killed pretty easily.

Speccing into Safeguard instead of Vigilance seems like an even worse idea. Just another pointless glyph just like the Weaponmaster and Whirlwind ones.

I find Intervene to be more and more a tool to move from point A to point B quicker rather than something to protect someone else with. As a warrior you already take a crapload of damage from everything and soaking a whole swing from someone else can get you killed pretty easily.

Speccing into Safeguard instead of Vigilance seems like an even worse idea. Just another pointless glyph just like the Weaponmaster and Whirlwind ones.

I guess. Though Minor glyphs were pretty much pointless in the first place, I like the weaponmaster one personally